• Title/Summary/Keyword: Clearance flow

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Effects of Casing Shape on the Performance of a Small-sized Centrifugal Compressor

  • Kim, D.W.;Kim, H.S.;Kim, Youn-J.
    • International Journal of Air-Conditioning and Refrigeration
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    • v.11 no.3
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    • pp.132-139
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    • 2003
  • The effects of casing shapes on the performance and the interaction between an impeller and a casing in a small-sized centrifugal compressor are investigated. Especially, numerical analyses are conducted for the centrifugal compressor with both a circular casing and a volute one. The optimum design for each element (i.e., impeller, diffuser and casing) is important to develop an efficient and compact compressor using alternative refrigerant as working fluids. Typical rotating speed of the compressor is in the range of 40,000∼45,000 rpm. The impeller has backswept blades due to tip clearance and a vane diffuser has wedge type. In order to predict the flow pattern inside an entire impeller, vaneless diffuser and casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. For computations of compressible turbulent flow fields, the continuity and time-averaged Navier-Stokes equations are employed. To evaluate the performance of two types of casings, the static pressure recovery and loss coefficients are obtained for various flow rates. Also, static pressure distributions around casings are studied for different casing shapes, which are very important to predict the distribution of radial load. The static pressure around the casing and pressure difference between the inlet and outlet of the compressor are measured for the circular casing.

Effect of Debrisoquine on Renal Function in Rabbits (Debrisoquine이 가토신장기능(家兎腎臟機能)에 미치는 영향(影響))

  • Ko, Suk-Tai;Park, Jung-Hee
    • Journal of Pharmaceutical Investigation
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    • v.14 no.2
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    • pp.92-103
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    • 1984
  • The action of debrisoquine on renal function in rabbits was studied. 1. When debrisoquine was given into ear vein, it did not affect on renal functin with smaller doses of 0.1 or 0.3mg/kg, while with higher dose of 1.0mg/kg it elicited the significant decrease of urine flow, renal plasma flow and glomerular filtration rate, and the increase of filtration fraction, and at the same time sodium excreted in urine, FENa (fractional excretion of sodium) and osmolar clearance were significantly decreased, and then it exhibited the increase of $K^+/Na^+$ ratio and no changes of $T^cH_2O$. 2. Debrisoquine (1.0mg/kg), when injected repeatedly into a vein, produced a more marked decrease of urine flow. 3. Debrisoquine induced-antidiuretic action was not affected by pretreatment with phentolamine (2mg/kg, i.v.), alpha-sympathetic blocking agent. 4. Debrisoquine given intracerebroventricularly did not produce a significant change on renal function in dose of 0.1mg/kg. These results suggest that debrisoquine produce the antidiuretic effect in rabbit, and the mechanism of its action is due to dual actions that are the decrease of hemodynamic effect and the facilitation of reabsorption of sodium in renal tubules.

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Heat Transfer and Flow Characteristics by Trapezoid Rod Array in Impinging Jet System (충돌제트계에서 사다리형 로드 배열에 의한 열전달 및 유동특성)

  • 금성민
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.9
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    • pp.904-913
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    • 2001
  • The objective of this study was to investigate the characteristics of jet flow and heat transfer caused by trapezoid rods array in impinging jet system. In this study, trapezoid rods have been set up in front of flat plate to serve as a turbulence promoter. The bottom width of trapezoid rod was W=4, 8 mm and oblique angle were 80$^{\circ}$. The space from rods to the heating surface was C=1, 2, 4 mm, the pitch between each rods was P=30, 40, 50 mm, and the distance from nozzle exit to flat plate was H=100, 500 mm. This results were compared with the case without trapezoid rods. As a result, when rods are installed in front of the impinging plate, the acceleration of the jet flow and the eddies due to the rods seem to contribute to the heat transfer enhancement. Among test conditions, the heat transfer performance was best for the condition of W=8 mm, C=1 mm, P=30 mm and H/B=10. The maximum heat transfer rate is about 1.9 times larger than that without trapezoid rods.

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CFD Analysis of a Partial Admission Turbine Using a Frozen Rotor Method

  • Noh, Jun-Gu;Lee, Eun-Seok;Kim, Jinhan;Lee, Dae-Sung
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.861-866
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    • 2004
  • A numerical flow analysis has been performed on the partial admission turbine of KARI turbopump to support the aerodynamic and structural dynamic assessments. The flow-field in a partial admission turbine is essentially three dimensional and unsteady because of a tip clearance and a finite number of nozzles. Therefore the mixing plane method is generally not appropriate. To avoid heavy computational load due to an unsteady three dimensional calculation, a frozen rotor method was implemented in steady calculation. It adopted a rotating frame in the grid block of a rotor blade by adding some source terms in governing equations. Its results were compared with a mixing plane method. The frozen rotor method can detect the variation of flow-field dependent upon the blade's circumferential position relative to the nozzle. It gives a idea of wake loss mechanism starting from the lip of a nozzle. This wake loss was assumed to be one of the most difficult issues in turbine designers. Thus, the frozen rotor approach has proven to be an efficient and robust tool in design of a partial admission turbine.

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The Effect of Sohabhyangwon(蘇合香元) on Regional Cerebral Blood Flow and Area of Cerebral Infarction in the Experimentally induced Cerebral Infarction in Rats (소합향원(蘇合香元)이 실험적(實驗的) 뇌경색(腦梗塞) 흰쥐의 국소뇌혈류량(局所腦血流量) 및 경색(梗塞) 면적에 미치는 영향(影響))

  • Choi, Eun-Jeong;Shin, Gil-Cho;Lee, Won-Chul
    • The Journal of Korean Medicine
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    • v.18 no.1
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    • pp.456-469
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    • 1997
  • The cerebral infarction arised from occulsion of cerebral artery has a high mortality rate and fatal sequelae. Sohabhyangwon(蘇合香元) is generally regarded to have a effect of walking up the patient from unconsiousness and promoting the flow of Qj(氣) by warming channel. METHOD The purpose of this study is to find out the effections of Sohabhyangwon(蘇合香元) on regional cerebral blood flow and relative cerebral infarction area in the experimentally induced infartion in rats In this experiment, 12 Spraque-Dawley rats weighting 280-350g were used. Cerebral ischemia induced by intraluminal suture technique of Kozumi's and Zea-Longer's method. $Co_{2},\;O_2$, pH, arterial blood pressure in rats were checked by Blood Gas Analyzer every 30 minutes for 2 hours. And regional cerebral blood flow were checking by hydrogen clearance technique, cerebral infarcted area was megsured by Image Analysis System. RESULTS 1. During the experiment, $CO_{2},\;O_2$, pH, arterial blood pressure in rats had no change in both sample group and control group. 2. Cortical cerebral blood flow decreased at same rate in both sample group and control group after inducing cerebral infarction. 3. On comparison of relative cerebral infarcted area, Sohabhyangwon(蘇合香元) perfused group showed a significant decrease. CONCLUSION According to the result above, Sohabhyangwon has a protection effect on cranial nerve and-has no effect on cerebral blood flow.

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Simplified Clearance Formalities of Northeast Asia port (동북아 항만의 입출항 수속 간소화 방안)

  • Choi Hyung-Rim;Park Nam-Kyu;Park Young-Jae;Cho Jae-Hyung
    • Journal of Navigation and Port Research
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    • v.29 no.5 s.101
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    • pp.439-445
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    • 2005
  • Recently, owing to the increasing demand on the simplification of arrival and departure procedures, IMO's (International Maritime Organization) Facilitation Committee (FAL) is carrying out the standardization project of arrival and departure formalities and clearance form. Also, many port authorities of developed countries are making active researches for the smooth flow and efficiency of the information inbound and outbound ships by way of simplifying their formalities or through electronic means. However, this standardization project cannot be done by one country but by mutual cooperation among related nations. And to carry out this task, the first thing to be done is to standardize the formalities and document form, and to integrate information. To this end, this study has reviewed the model cases of advanced ports of developed countries with regard to their simplification and standardization efforts. And also we have analyzed the formalities and clearance form of the three countries Korea, China, and Japan. And then for the solution of common problems of three countries, this paper has suggested an ebXML-based Global Port B2B framework. Through this framework, we can reuse and automate the necessary information on the arrival and departure of ships, consequently realizing simplification, and laying a foundation for the introduction of e-commerce to the port industry.

Influence of Isoproterenol on Intra-renal Blood Flow in the Dog (개의 신내혈류(腎內血流)에 미치는 Isoproterenol의 영향(影響))

  • Park, Ki-Dong
    • The Korean Journal of Pharmacology
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    • v.5 no.2
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    • pp.141-148
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    • 1969
  • The direct effect of isoproterenol on renal function, when given intravenously, is usually obscured by its potent hypotensive action. To obviate the latter action, isoproterenol was infused directly into one renal artery of the dog, the other kidney serving as a control for the general action. And following results were obtained. In the first series of experiments, the directic action of isoproterenol was ascertained. $1.0\;{\mu}g/kg/min$. reduced on both kidneys the urine flow, clearances of PAH and creatinine, as well as the amount of sodium excreted, but the effect was weaker on the experimental side than on contralateral side. With $0.1\;{\mu}g/kg/min$., two cases among 6 experiments showed marked diuresis, two cases no apparent effect, and another two marked antidiuresis on the experimental kidney, whereas the contralateral kidney exhibited antidiuresis in all cases. Further reducing the dose unmasked the diuretic action on the ,experimental kidney. In another series, the effects of isoproterenol on the blood flow distribution within the kidney and on sodium concentration gradient within the kidney tissue were observed. $0.05\;{\mu}g/kg/min$ isoproterenol markedly increased the medullary plasma flow and slightly increased total renal plasma flow and glomerular filtration rate, along with concomitant increase in the amount of sodium excreted and osmolar clearance, and decrease in reabsorption of free water. Sodium concentration gradient markedly decreased in the experimental kidney, reaching 2/3 of the value observed in the contralateral kidney at the papilla. It is thus concluded that isoproterenol exerts a diuretic action, when infused directly into a renal artery, and the mechanism of the action rests on its hemodynamic action, substantiated as the increase in glomerular filtration and in the medullary blood flow, resulting in washout of hyperosmolality produced by the coutercurrent multiplier system.

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Effect of Relative Position of Vane and Blade on Heat/Mass Transfer Characteristics on Stationary Turbine Blade Surface (베인과 블레이드 사이의 상대위치 변화에 따른 터빈 블레이드 표면에서의 열/물질전달 특성)

  • Rhee, Dong-Ho;Cho, Hyung Hee
    • 유체기계공업학회:학술대회논문집
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    • 2004.12a
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    • pp.140-150
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    • 2004
  • In this study, the effect of relative position of the blade for the fixed vane has been investigated on blade surface heat transfer. The experiments were conducted in a low speed stationary annular cascade, and heat transfer of blade was examined for six positions within a pitch. Turbine test section has one stage composed of sixteen guide vanes and blades. The chord length of the tested blade is 150 mm and the mean tip clearance of the blade having flat tip is about $2.5\%$ of the blade chord. For the detailed mass transfer measurements on the blade surfaces, a naphthalene sublimation technique was used. The inlet flow Reynolds number is fixed to $1.5{\times}10^5$. Complex heat transfer characteristics are observed on the blade surface due to various flow characteristics, such as separation bubble, relaminarization, transition to turbulence and leakage vortices. The distributions of velocity and turbulence intensity change significantly with the relative position due to the blockage effect of the blade. This causes the variation of heat transfer patterns on the blade surface. The results show that the flow near the leading edge get highly disturbed and deflected toward the either side of the blade when the blade leading edge is positioned close to the trailing edge of the vane. Therefore, separation bubble disappears on the pressure side and overall heat transfer on the relaminarization region is increased. But, due to reduced tip gap flow at the upstream region, the effect of leakage flow on the upstream region of the blade surface is weakened. Thus, the heat transfer characteristics significantly change with the blade positions.

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Effect of Vane/Blade Relative Position on Heat/Mass Transfer Characteristics on the Tip and Shroud for Stationary Turbine Blade (고정된 터빈 블레이드의 베인에 대한 상대위치 변화가 끝단면 및 슈라우드의 열/물질전달 특성에 미치는 영향)

  • Rhee Dong-Ho;Cho Hyung-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.5 s.248
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    • pp.446-456
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    • 2006
  • The effect of relative position of the stationary turbine blade for the fixed vane has been investigated on blade tip and shroud heat transfer. The local mass transfer coefficients were measured on the tip and shroud fur the blade fixed at six different positions within a pitch. A low speed stationary annular cascade with a single turbine stage was used. The chord length of the tested blade is 150 mm and the mean tip clearance of the blade having flat tip is 2.5% of the blade chord. A naphthalene sublimation technique was used for the detailed mass transfer measurements on the tip and the shroud. The inlet flow Reynolds number based on chord length and incoming flow velocity is fixed to $1.5{\times}10^5$. The results show that the incoming flow condition and heat transfer characteristics significantly change when the relative position of the blade changes. On the tip, the size of high heat/mass transfer region along the pressure side varies in the axial direction and the difference of heat transfer coefficient is up to 40% in the upstream region of the tip because the position of flow reattachment changes. On shroud, the effect of tip leakage vortex on the shroud as well as tip gap entering flow changes as the blade position changes. Thus, significantly different heat transfer patterns are observed with various blade positions and the periodic variation of heat transfer is expected with the blade rotation.

Heat/Mass Transfer Characteristics on Stationary Turbine Blade and Shroud in a Low Speed Annular Cascade (II) - Tip and Shroud - (환형 캐스케이드 내 고정된 터빈 블레이드 및 슈라우드에서의 열/물질전달 특성 (II) - 끝단 필 슈라우드 -)

  • Lee Dong-Ho;Cho Hyung Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.4 s.235
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    • pp.495-503
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    • 2005
  • Experiments were conducted in a low speed stationary annular cascade to investigate local heat transfer characteristics on the tip and shroud and the effect of inlet Reynolds number on the tip and shroud heat transfer. Detailed mass transfer coefficients on the blade tip and the shroud were obtained using a naphthalene sublimation technique. The turbine test section has a single stage composed of sixteen guide vanes and blades. The chord length and the height of the tested blade are 150 mm and about 125 mm, respectively. The blade has flat tip geometry and the mean tip clearance is about $2.5{\%}$of the blade chord. The inlet flow Reynolds number based on chord length and incoming flow velocity is changed from $1.0{\times}10^{5}\;to\;2.3{\times}10^{5}.$ to investigate the effect of Reynolds number. Flow reattachment after the recirculation near the pressure side edge dominates the heat transfer on the tip surface. Shroud surface has very intricate heat/mass transfer distributions due to complex flow patterns such as acceleration, relaminarization, transition to turbulent flow and tip leakage vortex. Heat/mass transfer coefficient on the blade tip is about 1.7 times as high as that on the shroud or blade surface. Overall averaged heat/mass transfer coefficients on the tip and shroud are proportional to $Re_{c}^{0.65}\;and\;Re_{c}^{0.71},$ respectively.